JPS6312145A - Pattern-dimension measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the dimensions of a pattern highly accurately, by adjusting the scanning range and the scanning speed of an electron beam at every measurement of each pattern, providing an irradiation control device, by which the emissivity of the secondary electrons from an irradiated point is made to be 1, and suppressing charge-up. CONSTITUTION:An electron beam 1a from an electron gun 1 is projected on a pattern 3 to be measure on a wafer 2. Secondary electrons 3a emitted from each irradiated point of a semiconductor carrying the pattern 3 are trapped by a detector 4. The signal waveform of the electrons 3a is read in a signal processing means 5. At this time, the scanning range and the scanning speed of the electron beam are made to correspond to the pattern shape and the pattern material for every measurement of each pattern. There is provided an irradiation control device 10, by which the emissivity of the electrons 3a from the irradiated point is made to be 1. Thus, charge-up is suppressed, and the highly accurate measurement of the dimensions can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for measuring the dimensions of a pattern formed on a wafer during the manufacturing process of semiconductor devices, and in particular,
The present invention relates to a pattern dimension measuring device that measures with high precision using an electron beam.

[Prior Art] Conventionally, a scanning electron microscope has generally been used to inspect the dimensions of various patterns formed on an evaporator during the manufacturing process of semiconductor devices.

That is, an electron beam is scanned so as to intersect the pattern to be measured, a secondary electron signal emitted from each irradiated point is detected, and the waveform of the secondary electron signal is processed by a computer to determine the pattern to be measured. This is to calculate the line width. At this time, the acceleration voltage of the electron beam irradiated onto the pattern to be measured is usually about 1 kV, which means that in this acceleration range, the secondary electron emission rate of general materials with respect to the electron beam irradiation is This is because it becomes approximately 1. Note that the secondary electron emission rate here represents the ratio between the amount of electrons incident on the material and the amount of electrons emitted from the material, and when this ratio is 1, the balance of electrons is balanced and no charge remains in the material. On the other hand, in the case of electron beam irradiation where the secondary electron emission rate is not 1, charge-up occurs in the material, so the accumulated charge interacts with the incident electrons, and the trajectory of the electron beam is bent. As a result, the detected secondary electron signal is distorted and no longer corresponds to the shape of the pattern to be measured, and there is a risk that the error with the pattern dimension to be measured will increase. The acceleration voltage of the beam is 2
It is necessary to select the optimum accelerating voltage so that the secondary electron emission rate becomes 1.

[Problems to be solved by the invention] However, since the optimum accelerating voltage differs depending on the material, in the case of a pattern in which multiple types of materials coexist within the irradiation area of an electron beam with a specific accelerating voltage, Even if some materials are free from charge-up, other materials may be charged up, causing errors in the measured pattern dimensions.

Generally, the charge-up phenomenon of a material during electron beam irradiation occurs when the balance of electrons emitted to a certain area of the material is disrupted. It also depends on density, irradiation time, pattern shape, etc. For these reasons, the reality is that it is difficult to establish optimal electron beam irradiation conditions that do not cause charge-up by simply initializing the acceleration voltage of the electron beam as in the conventional method.

The present invention was made to solve these problems, and it is a pattern that suppresses charge-up and enables highly accurate dimensional measurement even for patterns in which multiple types of materials are mixed. The purpose is to provide a dimension measuring device.

[Means for Solving the Problems] The present invention provides an apparatus for measuring the dimensions of a semiconductor pattern formed on a substrate using an electron beam. This is a pattern dimension measuring device characterized by comprising means for adjusting the secondary electron emission rate from the irradiated point to 1 in accordance with the pattern shape and the pattern material.

[Function] The electron beam irradiation conditions can be controlled not only by initial setting of the accelerating voltage but also by controlling the scanning range and scanning speed in the beam path. In the present invention, after adjusting the accelerating voltage of the electron beam and setting it to an approximate voltage value that can suppress the charge-up of the pattern to be measured to the extent possible, Since the irradiation speed of the electron beam is adjusted according to changes in the material type and shape of the pattern existing in the pattern, it is possible to suppress charge-up of the pattern to be measured, which could not be prevented by selecting the electron beam acceleration voltage alone.

- [Examples] Hereinafter, the present invention will be described in detail with reference to Examples and the drawings.

FIG. 1 shows one of the pattern dimension measuring devices embodying the present invention.
This is a configuration diagram showing an example. In the figure, the measurement device irradiates an electron beam 1a emitted from an electron gun 1 onto a pattern 3 to be measured on a wafer 2, and collects secondary electrons 3a emitted from each irradiation point of the semiconductor forming the pattern 3. The size of the pattern 3 to be measured on the wafer 2 is measured by capturing the signal waveform of the secondary electrons with the detector 4 and reading them with the signal processing means 5. During the irradiation from the gun 1 to the wafer 2, it is focused by the condenser optical system 6 and the objective optical system 7, and is also refracted by the blanking coil 8 to avoid direct irradiation to the wafer 2.
Further, the pattern to be measured 3 is scanned by the deflection coil 9 so as to cross the pattern 3 to be measured.

A blanking controller 8a is connected to the blanking coil 8 so that the scanning range can be varied, and a deflection controller 9a is connected to the deflection coil 9 so that the scanning speed can be varied. The blanking controller 8a and the deflection controller 9a are
It is roughly connected to the irradiation control device 10 and is controlled by it.

The irradiation control device 10 determines a scanning range for each pattern to be measured, based on information on the material and shape of each pattern on the wafer 2, such that the optimum irradiation speed can be obtained in accordance with the pattern shape and material type. and scanning speed are input to the blanking controller 8a and the deflection controller 9a, while a synchronization signal is transferred to the signal processing means 5. As a result of the irradiation with the electron beam controlled in this manner, the secondary electron signal detected by the pattern to be measured is accurately read by the synchronized signal processing means 5, and highly accurate measurement is performed. Become.

[Effects of the Invention] As explained above, according to the present invention, after setting the acceleration voltage of the electron beam to an approximate value considered to be the optimum acceleration voltage, the dissipation time of the charges accumulated in the pattern to be measured is taken into consideration. At the same time, the electron beam irradiation speed is adjusted according to changes in the material type and shape of the pattern on the substrate.
Conventionally, it is possible to prevent patterns in which multiple types of materials coexist, which could not be prevented simply by selecting the accelerating voltage of the electron beam.
It is possible to provide a pattern dimension measuring device that can almost completely suppress charge-up and enable highly accurate dimension measurement.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention. 1...Electron gun 2...Wafer 3...Pattern 4...Detector 5...Signal processing means
6... Condenser optical system 7... Objective optical system 8
...Blanking coil 8a...Blanking controller 9...Deflection coil 9a...Deflection controller 10...Irradiation control II device

Claims (1)

[Claims] (1) In a device that measures the dimensions of a semiconductor pattern formed on a substrate using an electron beam, the scanning range and scanning speed of the electron beam are adjusted to correspond to the pattern shape and pattern material for each pattern measurement. A pattern dimension measuring device characterized by comprising means for setting a secondary electron emission rate from an irradiation point to 1.